Many methods are known for catalytic conversion from an olefin-containing hydrocarbon material with a zeolite-containing catalyst; and there are many reports relating to methods for producing ethylene and propylene through catalytic conversion from an olefin-containing hydrocarbon material with a zeolite-containing catalyst.
However, efficient, stable and long-lasting production of ethylene and propylene through catalytic conversion from an olefin-containing hydrocarbon material with a zeolite-containing catalyst was difficult for the following reasons.
Ethylene and propylene are intermediates in conversion from olefins to aromatic hydrocarbons in the presence of a zeolite catalyst, and they are converted into aromatic hydrocarbons through successive reaction. Accordingly, in case where ethylene and propylene are produced through catalytic conversion from an olefin-containing hydrocarbon material with a zeolite-containing catalyst, the activity of the catalyst and the reaction condition must be severely controlled for obtaining the product at high yield. Specifically, when the catalyst activity is too high or when the contact time is too long, then the produced ethylene and propylene would be converted into aromatic hydrocarbons through successive reaction. On the contrary, when the catalyst activity is too low or when the contact time is too short, then the yield of ethylene and propylene would be low.
On the other hand, olefins are highly reactive, and when an olefin-containing hydrocarbon material is subjected to catalytic conversion with a zeolite-containing catalyst, then a carbonaceous deposit may readily form on the surface of the catalyst (coking). Accordingly, during continuous conversion reaction, the catalyst may be degraded by coking (coking degradation), and the catalyst activity may soon lower.
The catalyst of which the catalytic activity has been lowered by coking degradation may be restored to its original catalytic activity generally by heating it in the presence of an oxygen-containing gas to thereby burn away the coke.
However, when the regeneration operation is repeated, then the catalytic activity could not be sufficiently recovered. This is because, in the above regeneration operation, steam is formed through the coke combustion, and when zeolite is heated in the presence of the steam, then aluminium that is an active point of zeolite is released from zeolite crystals and the catalyst thereby undergoes permanent degradation (regeneration degradation).
As in the above, especially coking may often occur in catalytic conversion from an olefin-containing hydrocarbon material with a zeolite-containing catalyst, and therefore frequent regeneration of the catalyst is necessary and regeneration degradation of the catalyst may occur very often.
Patent Document 1 discloses a method of converting a paraffin, an olefin and/or a cycloparaffin (naphthene) having at least 5 carbon atoms into an aromatic hydrocarbon, ethylene and propylene with a proton-type ZSM-5 catalyst. In the method, however, the aromatic hydrocarbon may be obtained at relatively high yield but the yield of ethylene and propylene is low.
Patent Document 2 discloses a method of converting an olefin and a paraffin having from 2 to 4 carbon atoms into an aromatic hydrocarbon, ethylene and propylene with a proton-type ZSM-5 catalyst. Also in the method, the aromatic hydrocarbon may be obtained at relatively high yield but the yield of ethylene and propylene is low.
Patent Documents 3 and 4 disclose a method of converting butene into ethylene and propylene with an aluminophosphate-type molecular sieve. Also in this method, however, the yield of ethylene and propylene is low.
Patent Document 5 discloses a method of producing ethylene and propylene by contacting a hydrocarbon material of a mixture of a paraffin and an olefin having at least 4 carbon atoms and having a specific composition, with a proton-type ZSM5 zeolite. In this method, however, since the degree of conversion is low, a large amount of the unreacted material must be recycled.
Patent Document 6 discloses a method of converting a hydrocarbon having from 3 to 20 carbon atoms into ethylene and propylene with a phosphorus-containing, specific proton-type ZSM5 zeolite. In this method, however, where an olefin is used as the starting material, only the initial performance in 1 minute after the material supply is confirmed.
The characteristic common to the above methods is that a proton-type zeolite is used. In general, the proton-type zeolite has a high acid strength, with which, therefore, ethylene and propylene may be readily successively converted into an aromatic hydrocarbon, and the yield of ethylene and propylene is difficult to increase. In addition, when an olefin-containing hydrocarbon material is used, it often causes coking degradation and regeneration degradation.
Patent Document 7 discloses a proton-free zeolite catalyst that differs from conventional proton-containing zeolite catalysts, and discloses a method of using the catalyst for converting a hydrocarbon material into ethylene, propylene and a monocyclic aromatic hydrocarbon.
The catalyst used in this method is effective in that it hardly undergoes regeneration degradation, but could not still solve the problem of coking degradation. Accordingly, when a hydrocarbon material that contains a large amount of an olefin is processed, then it often causes coking degradation.
Patent Document 8 discloses a method of converting an olefin having from 4 to 12 carbon atoms into ethylene and propylene, with a IB Group metal-containing, aprotic intermediate pore-size zeolite that has a silica/alumina molar ratio of from 200 to 5000.
[Patent Document 1] JP-A-49-41322
[Patent Document 2] JP-A-50-49233
[Patent Document 3] U.S. Pat. No. 4,527,001
[Patent Document 4] U.S. Pat. No. 4,613,721
[Patent Document 5] JP-A-3-27327
[Patent Document 6] JP-A-6-73382
[Patent Document 7] WO1996/013331
[Patent Document 8] WO2000/010948